One of the problems with early Quad systems was that they did not have digital signal processing and fast computer chips back them. True surround sound has only become technically feasible in the last few years. We can thank Mr. Dolby, for pushing his ideas in the movie market, where it was much more successful than in records or FM radio.

To set up a quad system, with four speakers and a normal stereo amplifier, the rear speaker mus be the difference between Left and Right, as mentioned above, and the front, center speaker must be the sum of Left and Right, L and R positives to speaker Positive and speaker negative to amplifier negatives, which are bussed together. I tried it, and it wasn't bad.